[GLSL]Transfer texture to fragment shader

**GloWondub** · 04-01-2010, 08:49 AM

Hello

I'm now transferring texture to fragment shader.

But it's still not working.

here is my (test)shader :

Code :

#extension GL_ARB_texture_rectangle : enable
 
uniform sampler2DRect depthTex;
 
void main(void)
{
	float depth=texture2DRect(depthTex,gl_FragCoord.xy).x;
        gl_FragColor = gl_Color; // c'est aussi simple que cela
	gl_FragDepth=float;
}

and here how i try to exchange data :

Code :

 program = LoadProgram(NULL, "test.frag");
glUseProgram(program);
		glActiveTexture (GL_TEXTURE1);
		glBindTexture (GL_TEXTURE_2D, txDepth);
		depthTexLoc = glGetUniformLocation(program, "depthTex");
		glBindTexture (GL_TEXTURE_2D, txDepth);
   		glUniform1i(depthTexLoc, 1);

some used fonctions :

Code :

#include &amp;lt;stdio.h&amp;gt;
 
#include &amp;lt;stdlib.h&amp;gt;
 
#include &amp;lt;string.h&amp;gt;
 
 
 
#include &amp;lt;GL/glew.h&amp;gt; /* utilisation de glew ! */
 
 
 
#include "loadprogram.h"
 
 
 
 
 
 
 
 
 
int ExtensionSupportee(const char *nom)
 
{
 
#ifndef __glew_h__
 
    const char *extensions = glGetString(GL_EXTENSIONS);
 
#endif
 
 
 
    if(
 
#ifdef __glew_h__
 
    glewIsSupported(nom)
 
#else
 
    strstr(extensions, nom) != NULL
 
#endif
 
    )
 
        return 1;
 
    else
 
    {
 
        fprintf(stderr, "extension %s non supportee\n", nom);
 
        return 0;
 
    }
 
}
 
 
 
 
 
int InitExtensions(void)
 
{
 
    int state = 1;
 
 
 
    if(!ExtensionSupportee("GL_ARB_shading_language_100") ||
 
       !ExtensionSupportee("GL_ARB_shader_objects") ||
 
       !ExtensionSupportee("GL_ARB_vertex_shader") ||
 
       !ExtensionSupportee("GL_ARB_fragment_shader")
 
       /* rajoutez ici les extensions que vous utiliserez */)
 
    {
 
        state = 0;
 
    }
 
 
 
    return state;
 
}
 
 
 
 
 
 
 
/* charge le code source d'un shader */
 
static char* LoadSource(const char *filename)
 
{
 
    char *src = NULL;   /* code source de notre shader */
 
    FILE *fp = NULL;    /* fichier */
 
    long size;          /* taille du fichier */
 
    long i;             /* compteur */
 
 
 
 
 
    /* on ouvre le fichier */
 
    fp = fopen(filename, "r");
 
    /* on verifie si l'ouverture a echoue */
 
    if(fp == NULL)
 
    {
 
        fprintf(stderr, "impossible d'ouvrir le fichier '%s'\n", filename);
 
        return NULL;
 
    }
 
 
 
    /* on recupere la longueur du fichier */
 
    fseek(fp, 0, SEEK_END);
 
    size = ftell(fp);
 
 
 
    /* on se replace au debut du fichier */
 
    rewind(fp);
 
 
 
    /* on alloue de la memoire pour y placer notre code source */
 
    src = malloc(size+1); /* +1 pour le caractere de fin de chaine '\0' */
 
    if(src == NULL)
 
    {
 
        fclose(fp);
 
        fprintf(stderr, "erreur d'allocation de memoire!\n");
 
        return NULL;
 
    }
 
 
 
    /* lecture du fichier */
 
    for(i=0; i&amp;lt;size; i++)
 
        src[i] = fgetc(fp);
 
 
 
    /* on place le dernier caractere a '\0' */
 
    src[size] = '\0';
 
 
 
    fclose(fp);
 
 
 
    return src;
 
}
 
 
 
 
 
GLuint LoadProgram(const char *vsname, const char *psname)
 
{
 
    GLuint prog = 0;
 
    GLuint vs = 0, ps = 0;
 
    GLint link_status = GL_TRUE;
 
    GLint logsize = 0;
 
    char *log = NULL;
 
 
 
 
 
    /* verification des arguments */
 
    if(vsname == NULL &amp;&amp; psname == NULL)
 
    {
 
        fprintf(stderr, "creation d'un program demande, mais aucuns "
 
                        "noms de fichiers source envoye, arret.\n");
 
 
 
        return 0;
 
    }
 
 
 
 
 
    /* chargement des shaders */
 
    if(vsname != NULL)
 
    {
 
        vs = LoadShader(GL_VERTEX_SHADER, vsname);
 
        if(vs == 0)
 
            return 0;
 
    }
 
    if(psname != NULL)
 
    {
 
        ps = LoadShader(GL_FRAGMENT_SHADER, psname);
 
        if(ps == 0)
 
        {
 
            if(glIsShader(vs))
 
                glDeleteShader(vs);
 
            return 0;
 
        }
 
    }
 
 
 
 
 
    /* creation du program */
 
    prog = glCreateProgram();
 
 
 
    /* on envoie nos shaders a notre program */
 
    if(vs)
 
        glAttachShader(prog, vs);
 
    if(ps)
 
        glAttachShader(prog, ps);
 
 
 
    /* on lie le tout */
 
    glLinkProgram(prog);
 
 
 
    /* on verifie que tout s'est bien passe */
 
    glGetProgramiv(prog, GL_LINK_STATUS, &amp;link_status);
 
    if(link_status != GL_TRUE)
 
    {
 
        glGetProgramiv(prog, GL_INFO_LOG_LENGTH, &amp;logsize);
 
        log = malloc(logsize + 1);
 
        if(log == NULL)
 
        {
 
            glDeleteProgram(prog);
 
            glDeleteShader(vs);
 
            glDeleteShader(ps);
 
 
 
            fprintf(stderr, "impossible d'allouer de la memoire!\n");
 
            return 0;
 
        }
 
        memset(log, '\0', logsize + 1);
 
        glGetProgramInfoLog(prog, logsize, &amp;logsize, log);
 
 
 
        fprintf(stderr, "impossible de lier le program :\n%s", log);
 
 
 
        free(log);
 
        glDeleteProgram(prog);
 
        glDeleteShader(vs);
 
        glDeleteShader(ps);
 
 
 
        return 0;
 
    }
 
 
 
    /* les shaders sont dans le program maintenant, on en a plus besoin */
 
    glDeleteShader(vs);
 
    glDeleteShader(ps);
 
 
 
    return prog;
 
}
 
 
 
 
 
GLuint LoadShader(GLenum type, const char *filename)
 
{
 
    GLuint shader = 0;
 
    GLsizei logsize = 0;
 
    GLint compile_status = GL_TRUE;
 
    char *log = NULL;
 
    char *src = NULL;
 
 
 
    /* creation d'un shader de sommet */
 
    shader = glCreateShader(type);
 
    if(shader == 0)
 
    {
 
        fprintf(stderr, "impossible de creer le shader\n");
 
        return 0;
 
    }
 
 
 
    /* chargement du code source */
 
    src = LoadSource(filename);
 
    if(src == NULL)
 
    {
 
        /* theoriquement, la fonction LoadSource a deja affiche un message
 
           d'erreur, nous nous contenterons de supprimer notre shader
 
           et de retourner 0 */
 
 
 
        glDeleteShader(shader);
 
        return 0;
 
    }
 
 
 
    /* assignation du code source */
 
    glShaderSource(shader, 1, (const GLchar**)&amp;src, NULL);
 
 
 
 
 
    /* compilation du shader */
 
    glCompileShader(shader);
 
 
 
    /* liberation de la memoire du code source */
 
    free(src);
 
    src = NULL;
 
 
 
    /* verification du succes de la compilation */
 
    glGetShaderiv(shader, GL_COMPILE_STATUS, &amp;compile_status);
 
    if(compile_status != GL_TRUE)
 
    {
 
        /* erreur a la compilation recuperation du log d'erreur */
 
 
 
        /* on recupere la taille du message d'erreur */
 
        glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &amp;logsize);
 
 
 
        /* on alloue un esapce memoire dans lequel OpenGL ecrira le message */
 
        log = malloc(logsize + 1);
 
        if(log == NULL)
 
        {
 
            fprintf(stderr, "impossible d'allouer de la memoire!\n");
 
            return 0;
 
        }
 
        /* initialisation du contenu */
 
        memset(log, '\0', logsize + 1);
 
 
 
        glGetShaderInfoLog(shader, logsize, &amp;logsize, log);
 
        fprintf(stderr, "impossible de compiler le shader '%s' :\n%s",
 
                filename, log);
 
 
 
        /* ne pas oublier de liberer la memoire et notre shader */
 
        free(log);
 
        glDeleteShader(shader);
 
 
 
        return 0;
 
    }
 
 
 
    return shader;
 
}

but i always get 0 values.

so i try this :

Code :

#extension GL_ARB_texture_rectangle : enable
 
uniform float alpha;
void main(void)
{
 
gl_FragColor = gl_Color; // c'est aussi simple que cela
gl_FragDepth=alpha;
}

with this :

Code :

 program = LoadProgram(NULL, "test.frag");
glUseProgram(program);
lphaParam = glGetUniformLocation(program, "alpha");
   		glUniform1i(alphaParam, 0.666);

still give me 0.

any idea?

**pjcozzi** · 04-01-2010, 08:56 AM

Since you are using sampler2DRect, instead of sampler2D, your call to glBindTexture should target GL_TEXTURE_RECTANGLE instead of GL_TEXTURE_2D. Also, make sure your texture coordinates are in the range [0, w] and [0, h], where w and h are the width and height of the texture, respectfully.

Regards,
Patrick

**Bruce Wheaton** · 04-01-2010, 09:43 AM

And also your shader doesn't look right.

You're sampling the texture, and using it to make a float 'depth' variable, but you don't then use that to set any outputs. You set the fragment color to the incoming color, and I can't tell what you're setting the depth too - surprised that isn't a syntax error. Does your shader even compile?

Bruce

**GloWondub** · 04-02-2010, 09:17 AM

@pjcozzi : right thx a lot for that.
@bruce : that's just a transcription error.

ok, i try other different way to transfer data.

i succed to transfer float like this :

Code :

uniform float alpha;
void main(void)
{
 
	gl_FragColor = gl_Color; // c'est aussi simple que cela	
	gl_FragDepth=alpha;
}

with this part of code before rendering:

Code :

glUseProgram(program);
glUniform1f(glGetUniformLocation(program,"alpha"),0.666);

but in any way i cannot passed Texture data :

Code :

uniform sampler2D depthTex;
varying float depth;
void main(void)
{
	depth=texture(depthTex,vec2(0,0)[0]);
	gl_FragColor = gl_Color; // c'est aussi simple que cela
	if(gl_FragCoord.z<=depth)
		gl_FragDepth=0.99;
}

Code :

glUseProgram(program);
		glActiveTexture (GL_TEXTURE1);
		glBindTexture (GL_TEXTURE_2D, txDepth[(j+1)%2]);
		depthTexLoc = glGetUniformLocation(program, "depthTex");
		glBindTexture (GL_TEXTURE_2D, txDepth[(j+1)%2]);	
   		glUniform1i(depthTexLoc, 1);

i ALWAYS have the value 1.0000 in depth.

**pjcozzi** · 04-02-2010, 09:26 AM

This line is suspect:

Code :

depth=texture(depthTex,vec2(0,0)[0]);

The second argument is the texture coordinate used to read the texture. vec2(0, 0) is the bottom left of the texture. [0] is the x component (0). I'm actually surprised it compiles. I assume the scalar 0 is getting converted back to vec2(0, 0). Regardless, you are getting the same value out of the texture because you are always reading from the same location.

Regards,
Patrick

**Alfonse Reinheart** · 04-02-2010, 09:59 AM

There's also the fact that "depth" is a varying. You can't set varyings in a fragment shader (which is one reason why the explicit in/out distinction in 1.3 and above is so nice).

**GloWondub** · 04-02-2010, 10:04 AM

ok i correct it.

before there is no error in compilation.

so i try this :

Code :

uniform sampler2D depthTex;
 
varying float depth;
void main(void)
{
	depth=texture(depthTex,vec2(0,0))[0];
	gl_FragColor = gl_Color; // c'est aussi simple que cela
	if(gl_FragCoord.z<=depth)//(depth+bias))
		gl_FragDepth=0.99;
}

and this

Code :

uniform sampler2D depthTex;
varying float depth;
void main(void)
{
	depth=texture(depthTex,gl_FragCoord.xy)[0];
	gl_FragColor = gl_Color; // c'est aussi simple que cela
	if(gl_FragCoord.z<=depth)
		gl_FragDepth=0.99;
 
}

without any change in results or any errors

I'm currently searching example of code where a texture is transfered and try to compile and execute it.

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